Network Working Group C. Farrell
Request for Comments: 1712 M. Schulze
Category: Experimental S. Pleitner
D. Baldoni
Curtin University of Technology
November 1994
DNS Encoding of Geographical Location
Status of this Memo
This memo defines an Experimental Protocol for the Internet
community. This memo does not specify an Internet standard of any
kind. Discussion and suggestions for improvement are requested.
Distribution of this memo is unlimited.
Abstract
This document defines the format of a new Resource Record (RR) for
the Domain Naming System (DNS), and reserves a corresponding DNS type
mnemonic and numerical code. This definition deals with associating
geographical host location mappings to host names within a domain.
The data shown in this document is fictitious and does not
necessarily reflect the real Internet.
1. Introduction
It has been a long standing problem to relate IP numbers to
geographical locations. The availability of Geographical location
information has immediate applications in network management. Such
information can be used to supplement the data already provided by
utilities such as whois [Har85], traceroute [VJ89], and nslookup
[UCB89]. The usefulness and functionality of these already widely
used tools would be greatly enhanced by the provision of reliable
geographical location information.
The ideal way to manage and maintain a database of information, such
as geographical location of internet hosts, is to delegate
responsibility to local domain administrators. A large distributed
database could be implemented with a simple mechanism for updating
the local information. A query mechanism also has to be available
for checking local entries, as well as inquiring about data from
non-local domains.
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RFC 1712 DNS Encoding of Geographical Location November 19942. Background
The Internet continues to grow at an ever increasing rate with IP
numbers allocated on a first-come-first-serve basis. Deciding when
and how to setup a database of geographical information about
internet hosts presented a number of options. The uumap project
[UU85] was the first serious attempt to collect geographical location
data from sites and store it centrally. This project met with
limited success because of the difficulty in maintaining and updating
a large central database. Another problem was the lack of tools for
the checking the data supplied, this problem resulted in some
erroneous data entering the database.
2.1 SNMP:
Using an SNMP get request on the sysLocation MIB (Management
Information Base) variable was also an option, however this would
require the host to be running an appropriate agent with public read
access. It was also felt that MIB data should reflect local
management data (e.g., "this" host is on level 5 room 74) rather than
a hosts geographical position. This view is supported in the
examples given in literature in this area [ROSE91].
2.2 X500:
The X.500 Directory service [X.500.88] defined as part of the ISO
standards also appears as a potential provider of geographical
location data. However due to the limited implementations of this
service it was decided to defer this until this service gains wider
use and acceptance within the Internet community.
2.3 BIND:
The DNS [Mock87a][Mock87b] represents an existing system ideally
suited to the provision of host specific information. The DNS is a
widely used and well-understood mechanism for providing a distributed
database of such information and its extensible nature allows it to
be used to disseminate virtually any information. The most commonly
used DNS implementation is the Berkeley Internet Name Domain server
BIND [UCB89]. The information we wished to make available needed to
be updated locally but available globally; a perfect match with the
services provided by the DNS. Current DNS servers provide a variety
of useful information about hosts in their domain but lack the
ability to report a host's geographical location.
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RFC 1712 DNS Encoding of Geographical Location November 19943. RDATA Format
MSB LSB
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
/ LONGITUDE /
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
/ LATITUDE /
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
/ ALTITUDE /
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
where:
LONGITUDE The real number describing the longitude encoded as a
printable string. The precision is limited by 256 charcters
within the range -90..90 degrees. Positive numbers
indicate locations north of the equator.
LATITUDE The real number describing the latitude encoded as a
printable string. The precision is limited by 256 charcters
within the range -180..180 degrees. Positive numbers
indicate locations east of the prime meridian.
ALTITUDE The real number describing the altitude (in meters) from
mean sea-level encoded as a printable string. The precision
is limited by 256 charcters. Positive numbers indicate
locations above mean sea-level.
Latitude/Longitude/Altitude values are encoded as strings as to avoid
the precision limitations imposed by encoding as unsigned integers.
Although this might not be considered optimal, it allows for a very
high degree of precision with an acceptable average encoded record
length.
4. The GPOS RR
The geographical location is defined with the mnemonic GPOS and type
code 27.
GPOS has the following format:
<owner> <ttl> <class> GPOS <longitude> <latitude> <altitude>
A floating point format was chosen to specify geographical locations
for reasons of simplicity. This also guarantees a concise
unambiguous description of a location by enforcing three compulsory
numerical values to be specified.
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RFC 1712 DNS Encoding of Geographical Location November 1994
The owner, ttl, and class fields are optional and default to the last
defined value if omitted. The longitude is a floating point number
ranging from -90 to 90 with positive values indicating locations
north of the equator. For example Perth, Western Australia is
located at 32^ 7` 19" south of the equator which would be specified
as -32.68820. The latitude is a number ranging from -180.0 to 180.0.
For example Perth, Western Australia is located at 116^ 2' 25" east
of the prime meridian which would be specified as 116.86520. Curtin
University, Perth is also 10 meters above sea-level.
The valid GPOS record for a host at Curtin University in Perth
Western Australia would therefore be:
GPOS -32.6882 116.8652 10.0
There is no limit imposed on the number of decimal places, although
the length of the encoded string is limited to 256 characters for
each field. It is also suggested that administrators limit their
entries to the minimum number of necessary characters in each field.
5. Master File Format
Each host requires its own GPOS field in the corresponding DNS RR to
explicitly specify its geographical location and altitude. If the
GPOS field is omitted, a DNS enquiry will return no position
information for that host.
Consider the following example:
; Authoritative data for cs.curtin.edu.au.
;
@ IN SOA marsh.cs.curtin.edu.au. postmaster.cs.curtin.edu.au.
(
94070503 ; Serial (yymmddnn)
10800 ; Refresh (3 hours)
3600 ; Retry (1 hour)
3600000 ; Expire (1000 hours)
86400 ; Minimum (24 hours)
)
IN NS marsh.cs.curtin.edu.au.
marsh IN A 134.7.1.1
IN MX 0 marsh
IN HINFO SGI-Indigo IRIX-4.0.5F
IN GPOS -32.6882 116.8652 10.0
ftp IN CNAME marsh
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RFC 1712 DNS Encoding of Geographical Location November 1994
lillee IN A 134.7.1.2
IN MX 0 marsh
IN HINFO SGI-Indigo IRIX-4.0.5F
IN GPOS -32.6882 116.8652 10.0
hinault IN A 134.7.1.23
IN MX 0 marsh
IN HINFO SUN-IPC SunOS-4.1.3
IN GPOS -22.6882 116.8652 250.0
merckx IN A 134.7.1.24
IN MX 0 marsh
IN HINFO SUN-IPC SunOS-4.1.1
ambrose IN A 134.7.1.99
IN MX 0 marsh
IN HINFO SGI-CHALLENGE_L IRIX-5.2
IN GPOS -32.6882 116.8652 10.0
The hosts marsh, lillee, and ambrose are all at the same geographical
location, Perth Western Australia (-32.68820 116.86520). The host
hinault is at a different geographical location, 10 degrees north of
Perth in the mountains (-22.6882 116.8652 250.0). For security
reasons we do not wish to give the location of the host merckx.
Although the GPOS clause is not a standard entry within BIND
configuration files, most vendor implementations seem to ignore
whatever is not understood upon startup of the DNS. Usually this
will result in a number of warnings appearing in system log files,
but in no way alters naming information or impedes the DNS from
performing its normal duties.
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